Why is this while loop exiting after the first iteration?

Question

I have a very strange situation while trying to use a specific tool (esearch from the NCBI E-utilities suite) in a while loop. This is my input file, a list of strings, one per line:

$ cat transcripts.list 
NR_169596.1
NR_169595.1
NR_169594.1

I want to run the esearch command using each of those strings as an argument, so I do:

$ while read -r line; do echo "Line: $line"; esearch -db nucleotide -query "$line"; done <  transcripts.list 
Line: NR_169596.1
<ENTREZ_DIRECT>
  <Db>nucleotide</Db>
  <WebEnv>MCID_61bb689d20b59b3e2e2d405d</WebEnv>
  <QueryKey>1</QueryKey>
  <Count>1</Count>
  <Step>1</Step>
</ENTREZ_DIRECT>

This is a single result, not three, as you can see by the single echo that runs. The same thing works, however, if I use a bad practice for loop:

$ for line in $(cat transcripts.list); do echo "Line: $line"; esearch -db nucleotide -query "$line"; done
Line: NR_169596.1
<ENTREZ_DIRECT>
  <Db>nucleotide</Db>
  <WebEnv>MCID_61bb68cabbe98560233344a7</WebEnv>
  <QueryKey>1</QueryKey>
  <Count>1</Count>
  <Step>1</Step>
</ENTREZ_DIRECT>
Line: NR_169595.1
<ENTREZ_DIRECT>
  <Db>nucleotide</Db>
  <WebEnv>MCID_61bb68cad05f5825d75e3ace</WebEnv>
  <QueryKey>1</QueryKey>
  <Count>1</Count>
  <Step>1</Step>
</ENTREZ_DIRECT>
Line: NR_169594.1
<ENTREZ_DIRECT>
  <Db>nucleotide</Db>
  <WebEnv>MCID_61bb68cb6bdec5435b5a41cb</WebEnv>
  <QueryKey>1</QueryKey>
  <Count>1</Count>
  <Step>1</Step>
</ENTREZ_DIRECT>

Question: How is this possible? Even if there is some sort of bug in the specific esearch program, that shouldn't affect the looping, so why is the shell exiting after the first iteration? And how can the for work and the while fail? What do they do differently here?

---

Some more details.

1. Adding an echo in front of the esearch command makes the loop behave as expected, so this has to be related to the specific esearch command (but how can that break the shell loop?):

   $ while read -r line; do echo esearch -db nucleotide -query "$line"; done <  transcripts.list 
   esearch -db nucleotide -query NR_169596.1
   esearch -db nucleotide -query NR_169595.1
   esearch -db nucleotide -query NR_169594.1
   

2. There is nothing odd in the list itself, I can reproduce it with different lists and there are no hidden characters:

   $ od -c transcripts.list 
   0000000   N   R   _   1   6   9   5   9   6   .   1  \n   N   R   _   1
   0000020   6   9   5   9   5   .   1  \n   N   R   _   1   6   9   5   9
   0000040   4   .   1  \n
   0000044
   

3. I get the same behavior in bash and dash, so it can't be related to things like PIPEFAIL or anything like that. In any case, the exit status of the command is 0:

    while read -r line; do esearch -db nucleotide -query "$line"; echo "EXIT: $?"; done <  transcripts.list 
   <ENTREZ_DIRECT>
     <Db>nucleotide</Db>
     <WebEnv>MCID_61bb69e71191d1185543b24a</WebEnv>
     <QueryKey>1</QueryKey>
     <Count>1</Count>
     <Step>1</Step>
   </ENTREZ_DIRECT>
   

4. This is happening on a system running Ubuntu, bash, version 4.4.20(1)-release. You can install the efetch tool with sudo apt install ncbi-entrez-direct, if you want to try this out.

5. Works as expected in a loop using a different language. For instance, in perl:

   $ perl -ne 'chomp;system("esearch -db nucleotide -query \"$_\"")' transcripts.list 
   <ENTREZ_DIRECT>
     <Db>nucleotide</Db>
     <WebEnv>MCID_61bb6c68d8f66e4bb03f00e8</WebEnv>
     <QueryKey>1</QueryKey>
     <Count>1</Count>
     <Step>1</Step>
   </ENTREZ_DIRECT>
   <ENTREZ_DIRECT>
     <Db>nucleotide</Db>
     <WebEnv>MCID_61bb6c69947ca95fce4d4f0f</WebEnv>
     <QueryKey>1</QueryKey>
     <Count>1</Count>
     <Step>1</Step>
   </ENTREZ_DIRECT>
   <ENTREZ_DIRECT>
     <Db>nucleotide</Db>
     <WebEnv>MCID_61bb6c6a85c14642940393f9</WebEnv>
     <QueryKey>1</QueryKey>
     <Count>1</Count>
     <Step>1</Step>
   </ENTREZ_DIRECT>
   

Answer 1

This is probably because esearch exhausts its standard input; read and esearch are both reading from transcripts.list.

To fix that, change esearch’s standard input, e.g. esearch < /dev/null.

See I'm reading a file line by line and running ssh or ffmpeg, only the first line gets processed! in the Bash FAQ for details.